Biofuels from Saltwater Crops

Biofuels from Saltwater Crops

Fuel crop: A field of salicornia, a saltwater-tolerant plant, at a test plot in the north African country of Eritrea.

A project in the Middle East aims to make jet fuel from saltwater-tolerant crops grown in the desert. Researchers at the Masdar Institute in the United Arab Emirates are starting a two-square-kilometer demonstration farm that will combine fish and shrimp farming with the cultivation of mangrove trees and salicornia, a plant with oil-rich seeds that can be converted into fuel.

The goal is to produce biofuels without taking away land from food crops or using large amounts of fresh water, which are two of the major shortcomings of conventional biofuels, says Scott Kennedy, an associate professor at the Masdar Institute who is leading the project. The project is supported by several major companies: Boeing, Etihad Airways (the national airline of the UAE), and UOP Honeywell, which will supply technology for converting the biomass to chemical precursors and fuels. The Masdar Institute is part of a zero-emissions city being built in Abu Dhabi, the largest emirate in the UAE.

Kennedy and his colleagues will refine a technique called integrated seawater agriculture. It begins with digging a canal from the sea. That canal delivers water to several stages in the system. First, the researchers pump saltwater into ponds or flow it past cages used for growing shrimp or fish. Ordinarily, such aquaculture is an “environmental disaster,” Kennedy says. The runoff contains large amounts of feces that can cause dangerous algae blooms, for example. But in the Masdar system, the researchers will use that effluent downstream to fertilize salicornia.

The salicornia is grown in saltwater-irrigated fields, and can be harvested like other crops, such as wheat or rice. The runoff from that irrigation, now saltier and still containing some effluent from the fish and shrimp, together with more water from the canal, is next fed to a stretch of planted mangrove trees, which can grow in that saltier water. The mangrove forest provides a barrier, so that none of the polluted water from the fish farm returns to the ocean. The leaves can also be used as food for the fish.

The oil-rich seeds of the salicornia can be pressed using processing similar to that used for other oil seed crops, such as sunflowers. That oil can then be modified by a proprietary UOP Honeywell process that makes it suitable for blending in jet fuel. The rest of the plant can then be further used to produce liquid fuels, or burned to produce steam for electricity generation.